• 中国科技论文统计源期刊
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Volume 47 Issue 4
May  2022
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Study on the reference range of angle between superior mesenteric artery and abdominal aorta in normal fetuses at 21-41 weeks of gestation

  • Corresponding author: ZHAN Xiao-lin, 345730028@qq.com
  • Received Date: 2021-06-05
    Accepted Date: 2021-12-24
  • ObjectiveTo measure the angle between superior mesenteric artery(SMA) and abdominal aorta(AA)(SMA-AA angle) to calculate its 95% reference value range, and explore its correlation with fetal gestational age(GA), head circumference(HC), abdominal circumference(AC) and femoral length(FL).MethodsThe single pregnancy pregnant women diagnosed by obstetric ultrasound examination in The Fourth Affiliated Hospital of Anhui Medical University from January to April 2021 were selected according to the inclusion criteria.The SMA-AA angle in each fetus was measured, and the correlation of the angle with gestational age, head circumference, abdominal circumference and femur length were investigated.ResultsA total of 260 fetuses were included in the study.The mean value of SMA-AA angle of normal fetuses at 21-41 weeks of gestation was(57.75±7.27)°(range from 40.90° to 73.60°), and the 95% reference range was 43.50°-72.00°.There was no significant correlation between the SMA-AA angle and fetal GA, HC, AC and FL(r=0.007, 0.025, 0.022 and 0.025, respectively, P>0.05).The reproducibility of ultrasound measurement of the SMA-AA angle of normal fetuses at 12-41 weeks of gestation was good(the number of data points outside the interval of 95% agreement of inter-observers was 2.86%, and the number of data points outside the interval of 95% agreement of intraobserver was 0.04%).ConclusionsThe SMA-AA angle in normal fetus at 21-41 weeks of gestation remains relatively stable, and is not significantly correlated with fetal GA, HC, AC and FL.
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  • [1] NGUYEN H, NAVARRO OM, GUILLERMAN RP, et al. Untwisting the complexity of midgut malrotation and volvulus ultrasound[J]. Pediatric Radiol, 2021, 51(4): 658. doi: 10.1007/s00247-020-04876-x
    [2] KIM SH. Doppler US and CT Diagnosis of Nutcracker Syndrome[J]. Korean J Radiol, 2019, 20(12): 1627. doi: 10.3348/kjr.2019.0084
    [3] WONG K, TASSEL DV, LEE J, et al. Making the diagnosis of midgut volvulus: Limited abdominal ultrasound has changed our clinical practice[J]. J Pediatr Surg, 2020, 55(12): 2614. doi: 10.1016/j.jpedsurg.2020.04.012
    [4] 唐贤朋, 陶若翎, 张兴镐, 等. 三维能量多普勒超声评价胎儿肠系膜上动脉和静脉的价值[J]. 浙江大学学报(医学版), 2019, 48(4): 453.
    [5] 郭习娟, 陈桂红, 王锟, 等. 胎儿肠旋转不良合并十二指肠扭转超声表现1例[J]. 中华超声影像学杂志, 2018, 27(3): 270. doi: 10.3760/cma.j.issn.1004-4477.2018.03.020
    [6] 刘敏, 丁小军, 杨洁, 等. 超声对孕早期肠系膜上动脉上翘征的观察及应用研究[J]. 当代医学, 2019, 25(30): 73. doi: 10.3969/j.issn.1009-4393.2019.30.030
    [7] DIDIER RA, DEBARI SE, OLIVER ER, et al. Secondary imaging findings aid in prenatal diagnosis and characterization of congenital diaphragmatic hernia: Role of an abnormal orientation of vascular structures and gallbladder position[J]. J Ultras Med, 2019, 38(6): 1449. doi: 10.1002/jum.14823
    [8] PARDINHAS C, DOCARMO C, GOMES C, et al. Nutcracker syndrome: A single-center experience[J]. Case Rep Nephrol Dial, 2021, 11(1): 48. doi: 10.1159/000512589
    [9] RIBEIRO FS, PUECH-LEO P, ZERATI AE, et al. Prevalence of renal vein compression(nutcracker phenomenon) signs in computed tomography angiography of healthy individuals[J]. J Vasc Surg Venous L, 2020, 8(6): 1058.
    [10] 许海兵, 沈孝翠, 吉玉刚. MSCT对肠系膜上动脉与腹主动脉之间的夹角与距离的研究[J]. 医学影像学杂志, 2018, 28(12): 2122.
    [11] LAIQUE SN, VOZZO CF, CHAHAL P. Superior mesenteric artery syndrome: An unusual cause of abdominal pain[J]. Cureus, 2020, 12(11): e11505.
    [12] ESMAT HA, NAJAH DM. Superior mesenteric artery syndrome caused by acute weight loss in a 16-year-old polytrauma patient: A rare case report and review of the literature[J]. Ann Surg, 2021, 65: 102284. doi: 10.1016/j.amsu.2021.102284
    [13] 袁涛, 霍天龙, 杜湘珂. 64排螺旋CT评价肠系膜上动脉腹主动脉夹角与肠系膜上动脉压迫性病变及腹部脂肪分布相关性[J/CD]. 中华临床医师杂志(电子版), 2013, 7(10): 4521.
    [14] 肖毅, 陆君阳, 徐徕, 等. 肠系膜上血管系统解剖特点的临床研究[J]. 中华外科杂志, 2019, 57(9): 673.
    [15] 姜书情. SMA血流方向对胎儿左侧先天性膈疝的诊断价值[D]. 合肥: 安徽医科大学, 2020.
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Study on the reference range of angle between superior mesenteric artery and abdominal aorta in normal fetuses at 21-41 weeks of gestation

    Corresponding author: ZHAN Xiao-lin, 345730028@qq.com
  • Department of Ultrasonography, The Fourth Affiliated Hospital of Anhui Medical University, Hefei Anhui 230000, China

Abstract: ObjectiveTo measure the angle between superior mesenteric artery(SMA) and abdominal aorta(AA)(SMA-AA angle) to calculate its 95% reference value range, and explore its correlation with fetal gestational age(GA), head circumference(HC), abdominal circumference(AC) and femoral length(FL).MethodsThe single pregnancy pregnant women diagnosed by obstetric ultrasound examination in The Fourth Affiliated Hospital of Anhui Medical University from January to April 2021 were selected according to the inclusion criteria.The SMA-AA angle in each fetus was measured, and the correlation of the angle with gestational age, head circumference, abdominal circumference and femur length were investigated.ResultsA total of 260 fetuses were included in the study.The mean value of SMA-AA angle of normal fetuses at 21-41 weeks of gestation was(57.75±7.27)°(range from 40.90° to 73.60°), and the 95% reference range was 43.50°-72.00°.There was no significant correlation between the SMA-AA angle and fetal GA, HC, AC and FL(r=0.007, 0.025, 0.022 and 0.025, respectively, P>0.05).The reproducibility of ultrasound measurement of the SMA-AA angle of normal fetuses at 12-41 weeks of gestation was good(the number of data points outside the interval of 95% agreement of inter-observers was 2.86%, and the number of data points outside the interval of 95% agreement of intraobserver was 0.04%).ConclusionsThe SMA-AA angle in normal fetus at 21-41 weeks of gestation remains relatively stable, and is not significantly correlated with fetal GA, HC, AC and FL.

  • 胎儿肠系膜上动脉(superior mesenteric artery, SMA)与腹主动脉(abdominal aorta, AA)的夹角异常与左侧不典型膈疝、肠旋转不良、中肠扭转、左肾静脉压迫综合征、肠系膜上动脉压迫综合征等畸形密切相关[1-7]。查阅国内外文献可见,目前关于SMA与AA夹角的报道主要关注人群是成人和儿童[3, 8-10],胎儿SMA与AA夹角的研究相对少见,不利于产前检查过程中检出与诊断上述畸形。本研究通过测量进行产检结果正常的胎儿SMA与AA夹角,计算其95%参考值范围,并探讨其与孕周、头围和腹围等参数的相关性和性别间差异,为胎儿期检出上述畸形提供影像学依据。

1.   资料与方法
  • 选择2021年1-4月于我院进行产科超声检查且检查结果正常的胎儿。纳入标准:(1)自然受孕;(2)孕龄20~41周(孕龄按照母体末次月经或孕8~10周超声测量头臀径计算);(3)单胎妊娠。排除标准:(1)产科Ⅲ级筛查明确胎儿存在结构异常;(2)超声图像上SMA与AA之间的解剖关系模糊(如孕妇皮下脂肪过厚所致),影响角度测量。该项研究通过医院伦理委员会伦理审核通过,检查前告知孕妇及家属,并签署知情同意书。

  • 产科筛查及诊断应用GE E8彩色超声诊断仪,探头型号RAB 6-D。孕妇取仰卧位或侧卧位,嘱平静呼吸后开始检查。首先,根据国际妇产科超声学会指南操作规程进行产科畸形排查,并记录胎儿生物学指标(双顶径、头围、腹围和股骨长)。按照胎儿性别分为男性胎儿组和女性胎儿组。然后,选取胎位为正枕后的胎儿,于胎儿旁矢状面显示AA长轴观,微调探头显示SMA自AA前壁发出。按“ZOOM”键局部放大图像,清晰显示SMA与AA的成角关系。角度测量过程中,尽量避免探头对孕妇腹壁加压。最后,分别以SMA和AA后中心引直线,测量SMA与AA的夹角(见图 1),每个胎儿测量3次(数值精确至0.01°),取平均值并记录。对夹角可能异常的病例,经2位副主任医师以上职称的产前诊断医生双盲诊断,取其一致结果;若存在争议,由第三位同等资质医生裁决。

  • 随机抽取参与研究的孕妇70例,由2名观察者按照上述方法分别测量SMA与AA的夹角。采用Bland-Altman法进行重复性检验,记录观察者之间、观察者自身2次测值,计数95%一致性界限外的数据点数及其百分比。

  • 采用t检验和Pearson相关分析。

2.   结果
  • 研究期间共计260例胎儿满纳入标准。参与研究的母体年龄21.00~37.00岁,平均(28.00±5.00)岁。胎儿孕龄21.70~40.14周,平均(26.11±3.93)周;头围183.00~351.00 mm,平均(241.92±42.20)mm;腹围169.00~371.00 mm,平均(221.80±45.48)mm;股骨长36.00~74.00 mm,平均(47.73±9.61)mm;胎儿性别比例男∶女=1.22∶ 1。

  • 孕21~41周胎儿SMA与AA的夹角符合正态分布(Z=1.26,P>0.05)。SMA与AA夹角范围为40.90°~73.60°,平均(57.75±7.27)°,95%参考值范围43.50°~72.00°;男性胎儿组平均(57.67±7.33)°,女性胎儿组平均(57.87±7.22)°, 2组间SMA与AA夹角平均值差异均无统计学意义(t=0.24, P>0.05)。

  • 孕21~41周胎儿的SMA与AA夹角与孕周、头围、腹围和股骨长均无相关性(r=0.007、0.025、0.022和0.025,P>0.05)(见图 2)。

  • 观察者A与B之间差值位于95%一致性界限区间外数据点数为2/70(2.86%),差值均数(4.02±3.34)°。观察者A 2次测数差值位于95%一致性界限区间外的数据点数为1/70(0.04%),最大差值4.80°,测值均数(2.15±1.07)°。这种测量偏倚幅度在临床上可以接受,故认为采用超声测量孕21~41周胎儿SMA与AA夹角有很好的可重复性(见图 3)。

3.   讨论
  • 成人和儿童SMA与AA夹角的测量正常值已有大量的研究数据发布,测量手段相对较多(如超声、DSA和CTA等)[11-13]。目前国内外对胎儿SMA与AA夹角的正常值范围鲜有报道。我们通过测量260例正常胎儿SMA与AA的夹角,并分析其与头围、腹围和股骨长之间的相关性,发布了孕21~41周胎儿SMA与AA夹角正常参考值范围的单中心数据,为今后研究胎儿左侧不典型膈疝、左肾静脉压迫综合征和肠系膜上动脉压迫综合征等相关畸形提供影像学数据支持。

    SMA是AA的第二个不成对分支,在腹腔干下方数毫米处的AA前壁发出,斜上足侧走行,给胰腺、十二指肠、空肠、回肠和部分结肠等供血[14]。由于SMA起始处变异较大,国内学者袁涛等[13]报道成人SMA与AA夹角为(48.79±25.85)°,我们的研究显示孕21~41周胎儿平均值为(57.75±7.27)°。由于难以提取到成人和儿童SMA与AA夹角的原始数据,无法进行胎儿、儿童和成人的均数比较,难以回答三类研究人群间SMA与AA夹角均值的差异是否有统计学意义。但上述研究报道的标准差来看,与成人测值相比,胎儿SMA与AA夹角测值变异度相对较小。推测可能与成人个体之间体重相差较大有一定的相关性。

    与大多数胎儿器官或结构的生长参数与孕龄呈正相关不同,研究结果显示胎儿SMA与AA夹角与头围、腹围和股骨长无显著相关性。推测主要是因为SMA与AA的夹角并不是某部独立器官或结构形态学参数的绝对值,而是一个描述SMA与AA之间相对空间关系的指标。换言之,随着孕周的增长,即使在腹腔脏器(如肝脏、胃泡和肠管等)快速生长的晚孕期,SMA与AA之间的夹角并没有相应地出现有统计学意义的增加或减少,而是保持相对恒定。鉴于孕周对夹角的影响程度较弱,提示后续对SMA与AA夹角异常相关畸形(如前所述)的研究过程中,需更多关注除孕周外其他因素对SMA与AA夹角的影响。

    研究SMA与AA的临床潜在应用价值在于提高产前对胎儿相关畸形的检出率和诊断准确率。比如国内张超学教授团队研究报道左侧不典型膈疝(疝内容物为小肠)中,由于小肠向胸腔移位,SMA与AA夹角显著增大[15]。当SMA与AA夹角过小时,SMA压迫十二指肠可导致十二指肠梗阻,压迫左肾静脉而导致胡桃夹综合征。理论上来讲,胎儿环状胰腺、肠旋转不良等都会导致SMA与AA的夹角发生改变。但是在可疑病例的诊断过程中,一方面不同种类畸形中SMA与AA夹角异常的角色和价值不尽相同,另一方面不同种类畸形中SMA与AA夹角的临界值可能也不一样。这些疑问尚待后续研究在各类疾病中进行个体化深入研究。

    本研究尚存在一些不足,主要体现在2个方面: 第一,受孕中晚期产检周期影响,纳入研究的胎儿孕周分布以孕20~25周和28~32周胎儿数目相对较多,其他孕周胎儿数目则相对较少。第二,本研究仅报道了孕21~41周胎儿SMA与AA参考值范围,尚未纳入孕12~20周胎儿数据,有待于将研究扩展至孕早中期。

    综上所述,孕21~41周正常胎儿SMA与AA夹角保持稳定,其95%参考值范围43.50°~72.00°,该夹角与胎儿孕龄、头围、腹围和股骨长无显著相关性。

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